1. Technical Field
The present invention is related to a locking device for a band in a safety belt of a passive vehicle safety belt system. A passive vehicle safety belt system comprises a movable fastening means for the band in the safety belt; a guide rail for the movable fastening means attached to the car body; a power transmission means attached to the fastening means for moving the fastening means; and reversible motor means for driving the power transmission means for moving the fastening means backward and forward between a neutral position and a locking position on the guide rail. The locking device comprises a lock casing attached to the car body adjacent the guide rail at the locking position of the fastening means for keeping the fastening means. The purpose of a passive vehicle safety belt system is to automatically secure a person, e.g. the driver, who takes a seat in the car, before the car is started.
2. Background Art
Passive vehicle safety belt systems of the type set forth above are previously known, for example through U.S. Nos. 3,830,518, 4,256,331, 4,345,781 and 4,354,696.
An essential problem in the design of passive systems is the braking of the driving motor, normally an electric motor, used for moving the fastening means between the neutral position and the locking position, when the fastening means is moved into the lock casing and stopped in the casing. The fastening means is stopped very abruptly in the lock casing by striking a stop surface, and this causes a heavy shock load on the power transmission means and the reversible motor means due to the kinetic energy accumulated in the reversible motor means. This shock load can cause damage to the reversible motor means and the power transmission means leading to functional disorder and need of repair, and thus reducing the reliability of the system.